class_docstr: Sanitize the names of model input and output vars to make sure
  that they are of the format as described in the NameSanitizer class; that is,
  of the format ``[a-zA-Z_][a-zA-Z0-9_]*``.
code: def apply(self, prog):
      sanitizer_vars = NameSanitizer(prefix="var_")
      sanitizer_ops = NameSanitizer(prefix="op_")
  
      # sanitize the input/output of the main block
      NameSanitizer.sanitize_block(
          prog.functions["main"],
          sanitizer_vars,
          sanitizer_ops,
          prog.main_input_types,
          sanitize_model_inputs_outputs_only=True,
      )
  
imports: import re
  import warnings
  from collections import OrderedDict
  from coremltools import _logger
  from coremltools.converters.mil.input_types import EnumeratedShapes, ImageType, Shape
  from coremltools.converters.mil.mil import Builder
  from coremltools.converters.mil.mil import Function, types
  from coremltools.converters.mil.mil.passes.graph_pass import AbstractGraphPass
  from coremltools.converters.mil.mil.passes.pass_registry import register_pass
label_desc: Use image node_id 1 for calling the sanitize_input_output_names obj's underlying member method code with example usage: obj.apply(prog) without return types